1. Field of the Invention
The present invention relates to a radio communication terminal and a reception control method that are employed in a radio communication system compatible with a broadcast service and/or a multicast service, for example.
2. Description of the Related Art
1xEV-DO (1x Evolution Data Only) communication system has been commercialized, and one of the system functions is a broadcast multicast service (BCMCS).
In the broadcast services a radio communication network is used, and a base station continuously transmits data in a connectionless form to all radio communication terminals within a service area (for example, a cell or a sector) of the base station. That is, the broadcast service is one form of services of “broadcasting.”
The multicast service is similar to the broadcast service. The multicast service is one form of a service in which broadcasting is performed so that only specific users among the radio communication terminals within the service area who have signed up for specified service information (for example, a fee-based service) can receive the data.
FIG. 1 is a diagram showing a broadcast data and user data transmission schedule in the 1xEV-DO communication system. FIG. 2 is a diagram showing a broadcast data cyclic transmission schedule in the 1xEV-DO communication system.
In the broadcast service provided by the 1xEV-DO communication system, unlike a unicast data communication, the base station distributes the same data for all the users requesting for the data (FIG. 1).
At this time, since the terminal can only receive the data but not transmit data, a user who can not receive a part of the data for some reason can not issue a request for retransmission of the data.
However, for such a user, the broadcast data (the data in the broadcast service) is repetitively distributed in a certain cycle (FIG. 2).
Therefore, the user who fails to receive the requested data continues to receive the data in the broadcast service until the requested data is distributed for the next time. During this period, the terminal transmits, at constant intervals, a BCMCS flow registration message indicating that the terminal is keeping on receiving the broadcast service.
Further, since the broadcast data are non-periodically transmitted to the terminal that is performing the broadcast service, as well as during data communication, power needs to be constantly supplied from a power source to a radio circuit (reception circuit), and a radio link (traffic channel, broadcast channel) needs to be constantly monitored. This state is called a continuous reception state.
In addition to the continuous reception state, a terminal at an idle state performs an operation called intermittent reception.
In the intermittent reception operation, the base station periodically transmits required information (for example, notice information and incoming call) to the terminal, at a timing that is determined in advance through negotiation between the terminal side and the base station side. As a result, the terminal halts the supply of power from the power source to the radio circuit until information of which destination is the terminal is received, so as to reduce power consumption (FIG. 3: intermittent reception).
Unlike CDMA2000 1x (Code Division Multiple Access) communication system in which interval of the intermittent reception is always constant, the interval of the intermittent reception in the 1xEV-DO communication system herein differs depending on whether a “PPP (Point to Point Protocol) session” is performed. In the CDMA2000 1x communication system or the 1xEV-DO communication system, since there is a possibility of having an incoming call when the PPP session is performed, the interval of the intermittent reception needs to be shortened.
Presently, the interval of the intermittent reception when the “PPP session” is performed is 5.12 seconds. When the “PPP session” is not performed in the 1xEV-DO communication system, since there is no possibility of having the incoming call, only whether area information of the base station is changed is checked. In this case, compared with the interval of 5.12 second, the intermittent reception interval is actually extended.
The broadcast service in the radio system is disclosed in JP-2004-531937A.
However, the above-described intermittent reception is performed in a radio communication terminal that supports only the 1xEV-DO communication system. In a radio communication terminal that supports both the CDMA2000 1x communication system and the 1xEV-DO communication system, intermittent reception that satisfies both communication systems needs to be performed.
Furthermore, in the radio communication terminal that supports both the CDMA2000 1x communication system and the 1xEV-Do communication system, and further shares a radio communication part in both communication systems (hereinafter, referred to as a hybrid terminal), timings of the intermittent reception in the two systems should not overlap with each other (coincide with each other). Thus, as shown in FIG. 4, the intermittent reception is alternately performed for about 2.5 seconds.
Furthermore, since preference is given to the CDMA2000 1x communication system in the hybrid terminal, as shown in FIG. 5, even during the communication performed by the 1xEV-DO communication system, a control of a radio communication section is shifted to the CDMA2000 1x communication system at the interval of 5.12 seconds.
In order to avoid this situation, a specification, in which a signal message compatible with the CDMA2000 1x communication system is transmitted as a message compatible with the 1xEV-DO communication system so as not to shift the control of the radio communication section to the CDMA2000 1x communication system as much as possible, is included in 1xEV-DO Rev.A. The 1xEV-DO Rev.A is an extended version of the 1xEV-DO communication system.
When this specification is satisfied, it is enough to perform the intermittent reception only in the 1xEV-DO communication system. However, the intermittent reception needs to be performed at the interval of 5.12 seconds, regardless of whether the “PPP session” is performed.
At this time, a tentative calculation of a period of time required for the distribution of data of accumulation type via the broadcast service is performed.
When a data size is 5 Mbyte, and a data rate for broadcast is 75 kbps (transfer rate of physical layer; 614.4 kbps, ratio of real data in the physical layer: 2/3, slot allocated to the broadcast data: 1/6), 5*1024*8/75≡550 seconds. That is, about 10 minutes is required to receive the data for one cycle.
As described above, according to the radio communication terminal in the related art, since the radio link needs to be constantly monitored until the data of which reception is failed in the broadcast service is again received (while waiting for retransmission), there are disadvantages that the power consumption is increased, and battery life is shortened.